1. Field of the Invention
The present invention relates to a Fresnel lens comprising a glass plate, a Fresnel lens body integrally formed on one surface of said glass plate, and a reflective layer formed on an annularly grooved surface of said lens body. The grooved surface serves as a non-spherical light converging reflector with reduced lens material instead of using a thick and bulk lens.
2. Brief Description of the Prior Art
A conventional Fresnel lens is shown in each of FIGS. 9 and 11. The Fresnel lens L.sub.6 shown in FIG. 9 includes a Fresnel lens body 31 of a plastic material with a reflective layer 33 formed on an annularly grooved surface 32, and a hard coating layer 34 provided on the opposite surface of the annularly grooved surface 32.
The Fresnel lens L.sub.6 is fabricated through the following steps. In a Fresnel lens mold 35, a plastic resin plate material P1 is placed. After being softened, the upper mold 37 is lowered and the plate material P1 is press-formed. After being cooled, the press-formed Fresnel lens body 31 is derived from the mold 35. On the annularly grooved surface 32, aluminum or the like is sputtered to form a reflective surface 33. Finally, a hard coating layer 34 is formed on the opposite surface of the annularly grooved surface 32.
FIG. 11 shows another Fresnel lens L.sub.7, in which a Fresnel lens body 39 of a photo-curing resin is integrally formed on a surface of a plastic plate 38. Then, a reflective layer 41 on an annularly grooved surface 40 and a hard coating layer 42 on the opposite surface of the plastic plate 38 are formed.
The Fresnel lens L.sub.7 is fabricated through the following steps. As shown in FIG. 12, a photo-curing resin layer is formed on a transfer surface 43 of the annularly grooved surface 40 of Fresnel lens body 39, and a plastic plate 38 is placed thereon. After hardening of the photo-curing layer by illuminating ultra-violet ray, the lens body 39 formed as an integral member with the plastic plate 38 is taken out from Fresnel mold 44. The reflective layer 41 is formed on annularly grooved surface 40. Finally, the hard coating layer 42 is formed on the opposite surface of the plastic plate 38.